Police today warned Devon parents to be on their guard against a sick social media challenge which encourages youngsters to cut themselves. At its most extreme, the so-called 'Blue Whale' challenge encourages teenage suicide.

The challenge originated in Russia, where there have been reports of youngsters taking their own lives as a result. Those viewing Blue Whale are set a series of daily challenges. They begin innocently, but quickly become more sinister.

It is understood that some schools have already been notified of the threat of Blue Whale.

Torbay-based online safety expert Sergeant Steve Shepherd, who works with the UK Safer Internet Centre, said although exact details of Blue Whale remain sketchy, police are taking the challenge seriously.

"It's important to keep this in perspective," he said. "But we are concerned, and we want people to be aware of this."